1. Field of the Invention
The present invention relates generally to an industrial controller device, and more particularly to an industrial controller device capable of very high-speed serial communication.
2. Description of the Related Art
In general, plants using industrial controller devices employ a communication mechanism in which, in the state in which N EIA-485 interface devices have been connected to one host device or a small number of host devices using a multi-drop method in a 1:N correspondence, industrial controller devices are connected to the N EIA-485 interface devices in a 1:1 correspondence, thereby exchanging binary data, messages or packets with the hosts.
EIA-485 interfaces are low-speed serial interfaces. Although the number of EIA-485 interfaces that can be connected using a multi-drop method is limited to about 32, they are widely used because they have simple wiring.
As plants gradually become more elaborate and complicated, the number of industrial controller devices increases, and communication performance close to real-time performance is required. Although high-speed communication is not required from the perspective of a controller device in a terminal stage, high-speed communication is positively required from the perspective of a host device. Accordingly, there is a need for a network architecture and a communication interface capable of high-speed data transfer. In this scheme, a high-speed communication architecture is used up to a host device and a communication interface device, and conventional EIA-485 communication is used between the communication interface device and an industrial controller. In particular, industrial Ethernet using an IP address and packet exchange-type high-speed Ethernet interface device has emerged as a high-speed communication architecture.
However, industrial Ethernet is not compatible with an existing design scheme using controller devices, such as PLCs, because it is based on IP addresses. For example, in the existing scheme, the number of industrial controller devices may be repeatedly increased using a multi-drop method that is available in EIA-485. However, if such industrial Ethernet is employed, Ethernet interface devices need to be added using a hub, a switch, a bridge, or a repeater having a plurality of extension ports, and the Ethernet interface devices need to be connected via a subnet including controller devices not supporting an IP scheme and an Ethernet gateway.
Speed and costs can be generally balanced by employing a new high-speed Ethernet interface between the host and the Ethernet gateway device and continuously using an existing low-speed serial interface between the Ethernet gateway device and existing controller devices.
However, the above case is problematic in that design and installation are complicated, different types of networks should be managed during operation, and it is difficult to find a location where an error has occurred.
If controller devices include an Ethernet interface, the controllers cannot be connected using a multi-drop method, but should be connected to ports of a hub or a switch. For example, in the case of the overall air-conditioning system of a high-rise building, a multi-port hub should be installed in each floor, and the multi-port hub should be connected to air-conditioning units having Ethernet interfaces distributed throughout in the floor via Ethernet cables. When the Ethernet cables are connected to the air-condition units over long distances, data transfer errors frequently occur and transmission speed is reduced because the Ethernet cables have a limited transmission length. As a result, the advantage of the high-speed transmission ability of the Ethernet interface is cancelled by the above deficiencies.